Different sizes of containers are available on the market, for example with different lengths and heights. When transporting containers using a tractor unit or truck and a semi-trailer, it is desirable to be able to load the containers onto the semi-trailers and unload them therefrom by means of a lifting device of the same. However, it is difficult to transport different combinations and sizes of containers on one and the same semi-trailer and at the same time provide a lifting device for all different combinations and sizes of containers within the scope of statutory dimensions of truck and trailer combinations. Besides there are different container dimensions and statutory dimensions of container transports in different countries. Prior art technique offers solutions to move the container lifting device on a semi-trailer, using, for instance, gear racks, hydraulic motors, chains, and horizontally arranged hydraulic cylinders, but these solutions are sensitive to dirt and expensive and/or have an unreliable function.